Applicant claims, under 35 U.S.C. xc2xa7119, the benefit of priority of the filing date of Jun. 17, 1998 of a German patent application, copy attached, Serial Number. 198 26 875.0, filed on the aforementioned date, the entire contents of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to a numerical control unit for machine tools or robots with a spatially separated input device, wherein the input device has at least one input means for user information, and wherein a consent signal is transmitted via a connecting line to the control unit. The invention further relates to a method for operating the numerical control unit.
2. Discussion of Related Art
It is known from German Utility Model G 82 36 366.8, that in addition to a control board, machine tools can have an additional mobile manual advance device for special functions. In most cases, an indicator device is a part of the control board so that the user can trigger and monitor all functions of the control unit of the machine from there. The mobile manual advance device is also called an electronic handwheel and makes it possible for the user to enter, for example, the advance for one or several machine shafts not only when he stands at the control board, but also if he is located at a largely arbitrary position. To make this possible, the mobile manual advance device has several keys, for example, for the selection of a shaft, and an angle encoder for realizing a handwheel. In this case, the connection between the manual advance device and the control unit is provided via a cable having the lines required for signal transmission. This embodiment of a manual advance device has the disadvantage that it has not been designed to tolerate errors.
A numerical control unit with a spatially separated operating device, which has a handwheel for entering setting commands, is known from DE 297 10 026. In this case, the transmission of the setting commands from the spatially separated operating device to the control unit takes place within a fixed time grid by means of a wireless transmission device in accordance with the DECT (Digital European Cordless Telephone) standard. There is no mechanical connection between the control unit and the operating device, for example by means of a cable.
This embodiment has the disadvantage that it can be interfered with particularly ease by the electromagnetic fields present in a machine shop. Therefore, when the operating device is used, there is the permanent danger of a malfunction of the machine, not only because of the failure of electrical components, but additionally also because of interference with the radio transmission.
Accordingly, efforts are increasingly being made for designing the control units of machine tools, including the input devices, to be tolerant of errors. This means that an error must not result in danger to the user or damage to the machine. This is generally achieved in that redundant systems are used, which perform self-checks and, as soon as an error has been discovered, perform an error treatment. As a rule, the machine is stopped for this, so that no movement of the machine components takes place anymore. In addition, an error report is issued in most cases, which identifies the detected error and thereby makes repairs easier.
Various guidelines already exist regarding the demands made on errorproof systems, in particular control units. EN (European Standard) 954-1 establishes that an error-proof Category 3 system does not change to an unsafe operational stage because of a single error, but continues to remain a safe system in spite of the error.
Input units, which are spatially separated from the control board of a control unit of a machine tool, already exist, wherein an emergency shut-off key, keys for selecting a shaft of the machine tool, a handwheel and further input means are provided. Consent keys are additionally provided in order to increase the avoidance of errors. The latter must be actuated simultaneously with the input means of the input device. It is intended to assure by means of the fact that the user is required to operate two keys for triggering a safety-related function, that the user cannot initiate a malfunction or an unsafe operational state of the machine by a single input.
In this connection it is disadvantageous that the user must operate several keys for a simple input. The many connecting lines between the control unit and the input device, which are required for passing on the input signals of the consent keys and other signals, are also disadvantageous.
It is therefore an object of the present invention to design an input device, which is spatially separated from a control unit, in such a way that a single error does not lead to the unsafe operation of the machine which is controlled by the control unit.
A second object of the present invention is to create a numerical control for machine tools with increased operational dependability and optimized mobile input devices, such as handwheels and keys, in regard to their operational dependability.
A third object of the present invention is that the manipulation of the input device should be as user-friendly as possible, for which reason special consent keys should be omitted.
A fourth object lies in making the input device as cost-effective as possible.
Each of the above objects are attained by one aspect of the present invention that involves a numerical control that includes a control unit and an input device connected to the control unit via a connecting line so as to be spatially separated from the control unit and wherein a consent signal is transmitted from the input device to the control unit via the connecting line. The input device includes an input/output component that generate signals, a first processor connected with the input/output component and a second processor connected with the input/output component and independent from the first processor. The second processor has a comparator device for comparing the generated signals for conformity. A shut-off signal generator is connected with the comparator device and, via connecting lines, with the control unit.
Each of the above objects are attained by a second aspect of the present invention that regards a method for the dependable operation of a spatially separated input device of a numerical control that includes inputting at an input device so as to generate output signals, supplying the output signals to at least two processors and checking the output signals or signals based on the output signals for conformity in a comparator device. The method further includes transmitting a first shut-off signal to a control unit if there is no conformity.
The input device in accordance with the present invention has the advantage that pre-processing of the input signals is performed already in the input device itself. Because of this it is already possible to determine from the input device whether there is a technical malfunction of the keys, switches or of the handwheel and, in case of a malfunction, it is possible to forward an appropriate error message to the control unit by means of the input device. Moreover, it is possible by means of this pre- processing by the input device to advantageously reduce the number of connection lines between the input device and the control unit, by means of which easier manipulation and a more cost-effective production result. Because of these measures for error monitoring, special consent keys can be omitted. The regular monitoring of the connection between the input device and the control unit is furthermore advantageous.
Further objects, advantages and details of the invention will become apparent from the ensuing description of an exemplary embodiment in conjunction with the accompanying drawings.